SUPARCO's Climate Change Study Program primarily addresses the issues concerned with parameters and processes responsible for climate change with a view to provide a better
understanding of the effects and behaviour of key trace gases in the atmosphere. The analysis includes both experimental and computational studies in order to assess the impact of climate change
on national, regional and global scale, so that vulnerable areas and adaptation options can be identified.

This study is based on aerosol data level-2 as obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua and Terra satellites and cloud data of Automatic
Picture Transmission (APT) onboard NOAA (12, 15, and 16) satellites. These data were obtained at different locations in Pakistan for the period 2000-2003. Aerosol Optical Thickness (AOT) was
studied for area covering 22-36° N, 60-68° E. The maximum value was in the range 0.2-0.6 at 22° N, 60-68° E over the Arabian Sea during the months of April-June. The reason for this is the fall
of atmospheric pressure over Asia due to intense surface heating compared to the pressure over cool seas in the south. The moist equatorial air moves northward under this pressure gradient, which
decreases the optical thickness. As the air moves northward, away from the equator, the Coriolis force becomes increasingly effective, so the winds are south and south-westerly over Pakistan.
Similarly aerosol optical thickness at 31° N, 60-80° E (inland over Pakistan) shows that it is in the range of 0.2-0.8. Like aerosols, clouds also affect weather, therefore, the APT cloud data
for the period 2000-2003 were used to study cloud cover over well distributed places of Pakistan, which implied that during this period the northern areas of Pakistan remained most cloudy and the
southern part of the country remained least cloudy in the winter and post monsoon seasons.

Seasonal study of aerosol shows that in monsoon season (Jun-Aug) value of AOT over the areas covering 22-31° N, 60-72° E is in the range 0.3-0.6 while in dry post monsoon (Sep-Nov)
and cold winter season (Dec-Feb) it is mostly in the range 0.7-0.8. The study of AOT at 36° N, 60-75° E (northern mountainous region) shows that most of the time it is in the range 0.2-0.4 in the
mentioned seasons implying that the atmosphere was not perfectly transparent. Since aerosols act as Cloud Condensation Nuclei (CCN), the upper region of Pakistan remained mostly cloudy in the
same period.

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Winter

Pre-monsoon

Monsoon

Post-monsoon

Long Term Trend in Total Ozone over Pakistan using TOMS Data for the Period 1979-2004

Column ozone also obtained from the American satellite, Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) instrument, which operated from November 1978 through early May 1993, and
later on data from the TOMS instrument on-board the Russian Meteor-3 satellite till Dec 1994 have been used to determine trends in total ozone over Pakistan. Both TOMS data records with spectral
range 311-380 nm, and spectral resolution 1 nm, provide global measurements of total column of ozone on daily basis. Ozone data from 1995 onwards were obtained from Earth Probe and Japanese
Advanced Earth Observation Satellite (ADEOS) measurements. However, data gap existed for the period between mid 1994 to mid 1995. The reprocessed (version 7) daily total ozone observations made
by these satellites over Pakistan (Karachi 24° N, 67° E, Lahore 31° N, 74° E, Quetta 31° N, 67° E, Chitral 35° N, 71° E) for the period from November 1978 till now have been used to investigate
total ozone trends. Long-term trend estimates obtained from linear multiple regression analysis show no significant ozone trend in the south of the country (Karachi). However, the measurement for
mid latitude (Lahore , Quetta) northern region (Chitral 35° N, 71° E) have shown negative trend in ozone.

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Trend over Karachi

Trend over Lahore

Trend over Quetta

Trend over Chitral

Troposphere Ozone

Surface measurements of ozone have been made in six major cities of Pakistan using ground based ozone analyzer ML-8810. In recent years, concerns over the concentration of surface
ozone have increased mainly due to the finding that the surface ozone concentration in rural /urban areas has increased during the past few years. Injury to the most sensitive species can occur
after exposure to 60-µg/m3 (30.58 ppb) ozone for 8 hours. Ozone has shown reducing resistance to disease in laboratory animals. In humans, eye irritation and an increased number of asthmatic
attacks, and improper performances of athletes have all been attributed to photochemical oxidant levels around 200 ug/m3 (101.93 ppb). Most of the ozone in the troposphere (lower sphere) is
formed indirectly by the action of sunlight on nitrogen dioxide. In addition to ozone (O3) photochemical reactions produced a number of oxidants including peroxyacetyl Nitrates (PAN), nitric acid
and hydrogen per oxide. The surface ozone ranges from 6-40 ppb at Karachi, 8.5-44 ppb at Lahore, 6-32 ppb at Islamabad, 11-24 ppb at Quetta, 3-33 ppb at Rawalpindi and 4-46 ppb at Peshawar.